Where were Acrocanthosaurus fossils found?

Fossils of Acrocanthosaurus have been recovered primarily from the Antlers Formation of Atoka County, Oklahoma (where J. Willis Stovall and Wann Langston Jr. excavated the type specimens) and the Twin Mountains Formation of Texas. An extraordinarily complete specimen nicknamed 'Fran' (NCSM 14345) is permanently exhibited at the North Carolina Museum of Natural Sciences.

When did Acrocanthosaurus live?

Acrocanthosaurus lived during the Early Cretaceous Period (Aptian to early Albian stages, approximately 113 to 110 million years ago), dominating coastal floodplain ecosystems and river deltas along the ancient Western Interior Seaway millions of years before Tyrannosaurus rex evolved.

Acrocanthosaurus - Size, High Spines, Diet & Fossil Facts

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Evolutionary Taxonomy & Cladistics

View Dinosaur Phylogeny

Phylogenetic classification of Acrocanthosaurus atokensis Stovall & Langston, 1950 based on peer-reviewed cladistic analyses of diagnostic skeletal synapomorphies.

Taxonomic Rank	Taxon / Clade	Diagnostic Context
Kingdom	Animalia	Monophyletic prehistoric clade
Phylum	Chordata	Monophyletic prehistoric clade
Clade	Dinosauria	Monophyletic prehistoric clade
Order	Saurischia (Lizard-Hipped Dinosaurs)	Characterized ancestrally by a triradiate pelvis with an anteriorly pointing pubis.
Suborder	Theropoda	Bipedal saurischian dinosaurs, historically dominated by carnivores and including the avian lineage.
Genus	Acrocanthosaurus	Monophyletic prehistoric clade
Species	Acrocanthosaurus atokensis Stovall & Langston, 1950	Specific authority designation

At a Glance & Apex Predatory Adaptations

How Big Was Acrocanthosaurus?

Early Cretaceous Apex Macropredator

Total Length10.0–11.5 m33–38 ft

Estimated Mass4.5–6.5 tonnes4,500–6,500 kg

Standing Height3.4–4.0 m11–13 ft at head/hips

Temporal Range113–110 MaAptian–Albian

Paleontological Profile: Acrocanthosaurus atokensis was an apex predator of Early Cretaceous North America. Reaching lengths up to 11.5 meters and weighing over 6 metric tons, it was characterized by tall neural spines along its vertebral column that rose up to 2.5 times the centrum height. Rather than supporting a thin sail, these spines anchored massive epaxial back and neck musculature inferred to have stabilized the head and neck during feeding and physical exertion when dealing with large herbivores like Sauroposeidon and Tenontosaurus.

Fossil Evidence & Trackways: Discovered in the Antlers Formation of Oklahoma and Twin Mountains Formation of Texas, Acrocanthosaurus is represented by well-preserved skeletons including "Fran" (NCSM 14345). In addition, trackways in the Glen Rose Formation along the Paluxy River in Texas preserve large theropod footprints that have been interpreted by researchers as evidence consistent with predator-prey tracking or interaction with sauropods, though direct predation cannot be confirmed from trackways alone.

Anatomy & Physical Characteristics

Acrocanthosaurus was the undisputed apex predator of Early Cretaceous North America. Reaching up to 11.5 meters in length, it was distinguished by tall neural spines along its neck, back, and tail that reached up to 2.5 times the height of the vertebrae.

These spines supported massive muscle ridges and connective tissue, anchoring powerful back and neck muscles used to grapple with giant sauropods, as famously recorded in the Paluxy River fossil trackways in Texas.

Diagnostic Morphological Traits

Heavy bipedal carnivore with a thick muscular dorsal ridge running from neck to tail and a long, low skull.

Comparative Scale & Biometrics

Anatomical dimensions relative to an average adult human (1.8 m / 6 ft tall)

Approx. 6.4× human length

Acrocanthosaurus (Length)10–11.5 m (32.8–37.7 ft)

Adult Human1.8 m (6.0 ft)

Length

10–11.5 m (32.8–37.7 ft)

Height

3.4–4 m (11.2–13.1 ft)

Estimated Mass

4.5–6.5 metric tons (9,921–14,330 lbs)

Diet & Feeding Ecology

All Carnivore Species

Trophic Guild: Carnivore

Hunted sauropods like Sauroposeidon and ornithopods like Tenontosaurus.

Paleobiology & Behavior

Apex pursuit predator that shared the Early Cretaceous coastal plain ecosystem with contemporary dromaeosaurids like Deinonychus and large ornithopods like Tenontosaurus. Trackway assemblages and body fossils indicate it operated as the dominant carnivore across these ancient river deltas.

Habitat & Ecological Biome

Prehistoric Depositional Setting

Broad coastal river deltas, tidal mudflats, and open floodplain forests.

Fossil Evidence & Specimen Records

Preserved Skeletal Material & Bonebeds

Spectacular complete specimen 'Fran' (NCSM 14345) mounted at the North Carolina Museum of Natural Sciences.

Discovery & Taxonomic Naming History

Year of Discovery / Description1940

Type Specimen Locality & FormationAntlers Formation, Atoka County, Oklahoma, United States

Excavated by J. Willis Stovall and Wann Langston Jr.; described in 1950.

Geological Era & Chronostratigraphy

Explore All Cretaceous Period Fauna

Cretaceous Period PeriodTemporal Interval: 113–110 Ma (million years ago)

The longest and final period of the Mesozoic Era, characterized by the rise of flowering plants, ceratopsians, hadrosaurs, tyrannosaurids, and concluding with the Chicxulub asteroid impact.

Where It Lived & Paleoenvironment

North America Dinosaurs

During the Mesozoic Era, continental drift progressively reconfigured land bridges, atmospheric currents, and regional precipitation regimes. Fossils of Acrocanthosaurus evidence its adaptation to the paleoenvironments of North America.

Paleogeographic RealmNorth America (North America)

Home to the fossil-rich Morrison Formation of the Late Jurassic and the Hell Creek and Dinosaur Park Formations of the Late Cretaceous.

Fossil Discovery Locality

Scientific Significance & Evolutionary Impact

The anatomical architecture of Acrocanthosaurus serves as a crucial benchmark in vertebrate paleontology, illustrating key adaptive radiations within Theropoda.

Phylogenetic Placement: Informs cladistic debates concerning the divergence, skull biomechanics, and skeletal evolution of Cretaceous Period fauna.
Paleoecological Guild: Documents trophic specialization (Carnivore) and predator-prey dynamics across its regional ecosystem.
Taphonomic Record: Spectacular complete specimen 'Fran' (NCSM 14345) mounted at the North Carolina Museum of Natural Sciences.

Frequently Asked Questions About Acrocanthosaurus

Scientifically verified answers based on peer-reviewed paleontological evidence.

Q1.How big was Acrocanthosaurus?

Acrocanthosaurus atokensis was one of the largest theropods in North American history, reaching adult lengths between 10.0 and 11.5 meters (33 to 38 feet), standing 3.4 to 4.0 meters (11 to 13 feet) tall, and weighing an estimated 4,500 to 6,500 kg (4.5 to 6.5 metric tons).

Q2.What were the tall spines on Acrocanthosaurus for?

The neural spines along the vertebrae of Acrocanthosaurus rose up to 2.5 times the height of the vertebral centra. Biomechanical and histological studies show they anchored massive epaxial back and neck musculature, providing stabilizing power to absorb vertical and lateral stresses when grappling with large, struggling prey.

Q3.What did Acrocanthosaurus eat?

Acrocanthosaurus was a large carnivorous theropod suited for preying on contemporary Early Cretaceous herbivores, including sauropods (such as Sauroposeidon) and ornithopods (such as Tenontosaurus). In the Glen Rose Formation of the Paluxy River, Texas, trackways showing large theropod footprints alongside sauropod paths have frequently been interpreted as evidence consistent with predator-prey interaction or tracking behavior, though trackways cannot definitively prove active predation.

Academic Literature & Peer-Reviewed References

Authoritative citations establishing the factual taxonomy, biometrics, and anatomy of Acrocanthosaurus.

The American Midland NaturalistView Publication
Stovall, J. W., & Langston, W. (1950). Acrocanthosaurus atokensis, a new genus and species of Lower Cretaceous Theropoda from Oklahoma. The American Midland Naturalist, 43(3), 696-728. https://doi.org/10.2307/2421859
Curated & Verified: 2026-09-24

Acrocanthosaurus

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